There is a strong desire for developing high-Q inductors at ever smaller sizes using existing integrated circuit (IC) manufacturing techniques. However, current state of the art techniques require modification to IC processing technologies that are impractical for one reason or another. For example, the industry has a long felt need for creating air core inductors or transformers on a substrate where the inductors are robust during fabrication. Unfortunately, air core conducting coils have been extremely difficult to produce due to their flimsy nature, rendering them impractical for production.
Typically inductors have been produced having solid cores. However, such techniques are not always amenable to producing air core inductors. For example, U.S. Pat. No. 6,249,039 to Harvey et al describes techniques for producing inductive components having a solid core. However, manufacturing such a component is difficult because the process requires placement of shaped conducting bands around the solid core.
U.S. Pat. No. 5,425,167 to Shiga et al offers similar techniques to Harvey that can be used to form inductive components having an air core. Unfortunately, Shiga also suffers from the same limitation as Harvey by requiring shaped conducting bands. Utilizing shaped bands require modification of IC manufacturing processes which can be a costly endeavor. Furthermore, an inductor or transformer produced by the Shiga techniques lack sufficient structural integrity. Such device can not be mass produced in a reliable, repeatable fashion because the bands can bend or deformed during or after manufacturing causing changes to the device's desirable electrical properties (e.g. high-Q value, reduce parasitic capacitance, or reduced mutual inductance).
U.S. Pat. No. 6,531,945 to Ahn et al offers different techniques to produce solid core inductors without requiring shaped bands. Ahn's approach allows the use of existing, known IC processes for building solid core inductors. However, the approach is unsuitable for air core inductors. Should one wish to employ Ahn's technique for an air core inductor, then one would have to remove the solid substrate core leaving behind a flimsy rectangular coil lacking structure integrity.
U.S. Pat. No. 6,429,764 to Karam et al offers a solution for creating an air core inductor. The Karam approach includes providing a sacrificial core material that supports arched conducting bands. Once the arched bands are formed, the core material can be removed leaving behind an air core conducting coil. Unfortunately, producing the described arches in a repeatable, reliable manner proves to be quite problematic using existing techniques.
Ideally, one should be able to produce inductive components having an air core using simple existing IC process techniques. What has yet to be appreciated is that a conducting coil having an air core can be produce easily using existing techniques while maintaining structural integrity of the conducting coil.
Thus, there is still a need for components having an air core conducting coil where the coil is supported.